1. Field of the Invention
The present invention relates generally to fluid reaction surfaces, and more specifically to a turbine blade with trailing edge cooling slots.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In a gas turbine engine, a hot gas flow is produced in the combustor and passed through the turbine to produce mechanical work in driving the rotor shaft. The turbine typically includes four stages of stator vanes and rotor blades to extract the maximum amount of energy from the flow. It is well known that, to increase the efficiency of the turbine and therefore the engine, a higher temperature gas flow can be passed into the turbine. However, the maximum allowable temperature passed into the turbine is generally a function of the material properties of the turbine airfoils and the amount of cooling of these airfoils.
In an industrial gas turbine (IGT) engine, efficiency is a major design factor for the engine. With the high cost of fuel to power the IGT, every increase in efficiency results in significant fuel savings because the engines burn a lot of fuel during the constant operation. The first stage turbine blades and stator vanes are exposed to the highest gas flow temperature in the turbine. As the turbine inlet temperature increases, the size of the first stage turbine blade increases. As the size of these blades grow, the prior art cooling circuits that produced adequate cooling becomes unacceptable.
In an IGT, long part life is also a major design factor due to the fact that an IGT typically operates continuously for 24,000 to 48,000 hours. Hot spots that occur on a portion of an airfoil can result in erosion and other damage to the airfoil that would result in a decrease in the performance of the part, reducing the efficiency of the engine. Hot spots occur where inadequate cooling occurs. Complex internal cooling circuitry has been proposed for providing convention cooling, impingement cooling and film cooling for the airfoils.
One portion of the IGT first stage turbine blade that has problems with inadequate cooling is the trailing edge blade tip. Typical prior art turbine blades have a tip corner on the trailing edge side of the blade that can be significantly under cooled, resulting in hot spots that lead to erosion damage and low performance.
It is therefore an object of the present invention to provide for a turbine blade with an improved trailing edge cooling circuit.
It is another object of the present invention to provide for a turbine blade with the elimination of the tip corner along the trailing edge.
It is another object of the present invention to provide for a large first stage turbine blade in an industrial gas turbine that will have an acceptable internal cooling circuit for the entire blade.